It’s impossible to change framerate for created timeline in Davinci Resolve. But I have one solution: you can find still frames by size (the 24th and 25th will be the same; and their sizes are same too).

Render video as tiff sequence (or exr, no matter) and save it into ‘root/tmp/<image_sequence>.tiff’

You don’t need to buy blackmagic hardware to make fullscreen playback 🙂
If you have 3 screens you can download this magnifier program (http://www.blacksunsoftware.com/screenmagnifier.html) and make third screen for its output! So, it will zoom you playback from small playback window to the third monitor.